1. Field
Some example embodiments relate to electro-absorption optical modulators that include graphene.
2. Description of the Related Art
Optical modulators are apparatuses for transmitting information by changing the characteristics of light, for example, light intensity or phase of the light. The optical modulator may operate according to a change of an electro-refraction or an electro-absorption caused by an electric current or a voltage applied to an optical waveguide through which the light passes, for example, an optical waveguide of a semiconductor material.
An electro-absorption optical modulator operates based on a change of a light-absorption rate caused by a change in a bandgap size due to the Franz Keldysh effect after applying a bias voltage to an optical waveguide.
In most conventional optical modulators, the characteristics of light are changed with respect to the light of a certain wavelength, and thus, an operation bandwidth of the optical modulators is narrow, that is, about 20 nm or less. In addition, manufacturing a relatively high speed optical modulator due to a resistance-capacitance (RC) delay may be difficult. In addition, since a modulation depth per unit length of the optical waveguide is relatively small, a size of the optical modulator may be increased in order to modulate the light sufficiently.
Graphene is a material having a two-dimensional hexagonal carbon structure. Graphene may be used instead of semiconductors and has a carrier mobility of about 200,000 cm2V-1s-1 at room temperature, which is one hundred times higher than that of silicon, and thus, may be used in a higher speed operation device, for example, an optical modulator.